1. Field of the Invention
The present invention relates to an imaging device used for a digital camera.
2. Background Arts
Now many digital cameras adopt a TTL photometry (Through The Lens photometry) system with high precision for a photometry to control exposure. This TTL photometry system measures brightness of a scene to be taken by using an output signal from an imaging device for taking the scene.
Many digital cameras also have an automatic flash device. The automatic flash device measures reflection of a flashlight from a subject with photo sensor, and automatically stops emission of the flashlight when detects that a quantity of the reflection of the flashlight reaches a predetermined level. Therefore, the automatic flash device prevents the subject from being illuminated so much with excessive emission of the flashlight and allows flash photography in a short-distance.
Recently, it is expected to adjust the quantity of the flashlight precisely by adopting the TTL photometry system even in the photography with the automatic flash device. Since the automatic flash device has to measure the reflection of the flashlight emitted instantaneously, quick response performance is required on a photo sensor. However, the imaging device cannot be used as the photo sensor of the automatic flash device because the imaging device takes time to storage and transfer signal charge. It is also considered to install a photo sensor inside a lens barrel, but the installation takes a lot of trouble.